A gramphone record is revolving with an angular velocity omega. A coin is placed at a distance `r` from the centre of the record. The static coefficient of friction is mu. The coin will revolve with the record if.

Options

A. `r=mugomega^(2)`
B. `rltomega^(2)/(mug)`
C. `rle(mug)/(omega^(2))`
D. `rge(mug)/(omega^(2))`

Answer

C

Explanation

When the disc spins the frictional force between the gramphone record and coin is `mumg`
The coin will revolve with record, if
`F_(frictionalgeF_(centripetal)`
`mumggemomega^(@)r`
`(mug)/(r)geomega^(2)` .